Model railroad electric locomotive sound system

ABSTRACT

An accessory includes a speaker mounted in the locomotive tender electrically driven by an audio frequency signal from one or more electronic sound generators simulating respectively a bell, escaping steam either from an engine exhaust, leakage or blowoff, and a whistle. The engine exhaust sound is timed by periodically grounding the radio frequency oscillator of a timing circuit for the escaping-steam-simulating generator by intermittently closing a switch in the circuit effected by rotation of a driver wheel of the locomotive. Selective controls enable the bell and whistle to be operated at will and further enable the nature of the sounds of the bell, exhaust and whistle to be modified. Direct current for the locomotive driving motor, the audio frequency signal to drive the speaker and the radio frequency signal to the locomotive-carried switch for timing the simulated engine exhaust are all simultaneously impressed on the two rails but electronic blocking components included in the circuit prevent the enginedriving direct current and the radio-frequency signaling current from interfering with the speaker operation and prevent the audio frequency signal and the radio frequency signal from leaking into the direct-current power circuit.

States Longnecker [72] Inventor: Robert H. Longneclter, Glen Mills, Pa. [73] Assignee: Pacific Fast Mail, Edmonds, Wash. [22] Filed: Mar. 8, 1971 21 Appl. No.: 121,701

[52] U.S. Cl ..46/232, 46/243 P, 46/217 [51] Int. Cl ....A63h 19/10, A63h l9/l4 [58] FieldofSearch ..46/216, 232, 243 P [56] References Cited UNITED STATES PATENTS 2,826,996 3/1958 Smith Primary Examiner-Louis G. Mancene Assistant ExaminerRobert F. Cutting Attorney-Robert W. Beach [57 ABSTRACT An accessory includes a speaker mounted in the locomotive tender electrically driven by an audio frequency signal from one or more electronic sound generators simulating respectively a bell, escaping steam either from an engine exhaust, leakage or blowoff, and a whistle. The engine exhaust sound is timed by periodically grounding the radio frequency oscillator of a timing circuit for the escaping-steam-simulating generator by intermittently closing a switch in the circuit effected by rotation of a driver wheel of the locomotive. Selective controls enable the bell and whistle to be operated at will and further enable the nature of the sounds of the bell, exhaust and whistle to be modified. Direct current for the locomotive driving motor, the audio frequency signal to drive the speaker and the radio frequency signal to the locomotive-carried switch for timing the simulated engine exhaust are all simultaneously impressed on the two rails but electronic blocking components included in the circuit prevent the engine-driving direct current and the radio-frequency signaling current from interfering with the speaker operation and prevent the audio frequency signal and the radio frequency signal from leaking into the direct-current power circuit.

17 Claims, 5 Drawing Figures Patented May 23, 1972 3,6fi4,060

2 Sheets-Sheet l Patented May 23, 1972 3,664,06U

2 Sheets-Sheet :3

m nii INVENTOR. ROBERT H. LON6NECKER ATTORNEY MODEL RAILROAD ELECTRIC LOCOMOTIVE SOUND SYSTEM A principal object of the present invention is to provide a single electronic sound system accessory for model railroad locomotives which can produce the sound of a bell, a whistle, or escaping steam either as chuffing while the locomotive is traveling or steam leakage when the engine is stopped, or steam blowoff.

A particular object is to provide an accessory by which any of these sounds produced will be very realistic, and which can be controlled to alter the tone, the volume and the duration.

Specifically it is an object to enable the sound of escaping steam to be simulated as chuffing of the locomotive in precise synchronism with the speed of the locomotive, as well as enabling the sound to be altered to simulate working under heavy load or light load.

A further object is to promote the realism of the sounds produced by emitting them from the locomotive.

It is also an object to enable the operator to control the tim ing and duration of the simulated bell, whistle and steam blowoff sounds at will.

An additional object is to enable such simulated locomotive sounds to be produced and controlled without interference with the propulsion of the locomotive and the ability of the operator to control its speed and direction of movement.

It is an object to provide such a locomotive sound system in which the sounds emanate from the locomotive without requiring any additional transmission wires or the use of radio transmission and reception, but simply by using the railway tracks as conductors.

FIG. 1 is a block circuit diagram including the circuitry for the locomotive driving power and for the several electronic sound-producing components.

FIG. 2 is a diagrammatic top perspective showing the circuitry in the locomotive including cam mechanism closing a switch periodically.

' FIG. 3 is a fragmentary horizontal section of a portion of a locomotive showing an alternative type of periodically closable switch mechanism viewed from line 33 of FIG. 4.

FIG. 4 is a fragmentary vertical section taken along line 4- 4 of FIG. 3.

FIG. 5 is a top perspective of stationary and portable control units.

Operating model trains have been available for a considerable period of time. In many instances such trains have been accurate scale replicas of the rolling stock of various railroads. Such model trains have been powered to be operated by remote controls at various speeds and, alternatively, in forward and reverse directions. Moreover, such trains have been operated over elaborate trackage systems. A principal deficiency of previous systems has been their inability to simulate realistic locomotive sounds such as the bell, the whistle and escaping steam.

Conventionally, a model train includes a locomotive 1 shown diagrammatically in phantom in FIG. 2, propelled by driving wheels 2 running on rails 3 and 4. A simulated steam locomotive has a tender 5, also shown in phantom perspective in FIG. 2, trailing behind the locomotive, which usually is disengageably attached to the locomotive. The driving wheels 2 of the locomotive are driven by an electric motor 6 turning a worm 7 which meshes with a worm gear 8, shown in FIGS. 3 and 4 as being secured on the axle 9 carrying the driving wheels 2.

Motive Power Power for the locomotive propulsive system and sound system is supplied from a conventional llO-volt alternating current supply source through a conventional plug 10, which is connected to the mainline switch 11 shown in the circuit of FIG. 1, and on the stationary control box of FIG. 5. The alternating current source supplies power for the direct-current power supply 76 which is of conventional type and may include a transformer, a full-wave rectifier, and a filter capacitor. Such DC power supply is connected through the throttle 13, which is a cascaded current amplifier, to the rails 3 and 4 by way of a wire 14 and a grounded wire 15. The DC power supply is also connected to ground.

Electrical power is supplied to the various components of the sound system accessory by a regulator circuit 16 which provides a constant-voltage direct-current source, such for example as lO volts, irrespective of considerable fluctuation in the voltage of the alternating current supply or differences in voltage of different supplies. Because of the large number of components of the sound system powered by such constant voltage direct-current supply, such power supply connections are not shown in FIG. 1. Also many of such circuit components are individually connected to ground, but for simplicity such ground connections also are not shown.

The speed of the motor 6 driving the locomotive driving wheels can be altered at will by movement of the speed-control potentiometer 17, which controls the current output of throttle 13. Such motor is of the reversible type. and its direction of rotation, and consequently the direction of rotation of the locomotive driving wheels, can be reversed at will by interchanging the leads to the rails 3 and 4 by shifting the reversing switch 18. The motor 6 is always connected in the same relationship to the rails 3 and 4 unless the locomotive is turned end for end.

Locomotive Construction The manner in which the connection is made between the rails 3 and 4 and the motor 6 can be conventional. The locomotive wheels are insulated from the locomotive frame on one side, and the tender wheels are insulated from the tender frame on the opposite side. The tender frame 19 thus constitutes one side of the motor circuit to which it is connected through a separable connector 20 and a wire 21, and the locomotive frame 22 constitutes the other side of the electrical circuit. Such components are indicated diagrammatically as electrical circuit components in FIG. 2. The locomotive frame and the tender frame are connected by an insulating mechanical drawbar-type coupling.

Sound Propagation In order to produce the most realistic locomotive sound propagation it is desirable both that the simulated sounds generated be of high fidelity and that the sounds emanate from the locomotive as their source. The simulated locomotive sounds are generated by electronic audio frequency signal synthesizing means for driving a speaker 23 carried by the model train, which conveniently can be mounted in the locomotive tender 5. One terminal of the speaker is connected by wire 24 to the frame of the tender in circuit with rail 3, and the other terminal of the speaker is connected by wire 25, connector 26 and wire 27 with the frame 22 of the locomotive which is in circuit with rail 4.

Through the connections mentioned above, the speaker 23 is connected in circuit with the rails 3 and 4 continually, as long as the locomotive l and tender 5 are coupled together, so that the connector 26 connects wire 25 in the tender with wire 27 in the locomotive. Electrolytic capacitors 28 are connected in back-to-back series relationship in the wire 24 between the speaker and the tender frame to provide a non-polarized capacitance for blocking flow to the speaker of direct current for energizing the driving motor 6 irrespective of the direction in which the direct current flows. The value of such capacitors is not critical but must be large enough to pass the lowest audio frequency signals from the sound system destined for the speaker.

Locomotive sounds are produced by the speaker 23 driven by audio frequency alternating current which may be composed of a blend of several audio frequency signals integrated by the mixer section 29 and amplified by the audio amplifier 30. Such mixer section may include a transformer mixing stack, the transformers of which correspond respectively to the several types of signals generated for the various locomotive sounds to be propagated. The intensity of the blended audio frequency signal can be adjusted by the main volume control potentiometer 31 to alter the overall volume of the sound emanating from the speaker 23.

A blocking capacitor 32, preferably of the electrolytic type, is interposed in the wire connecting the audio amplifier 30 to the wire 14 connected to one of the rails for the purpose of blocking flow to the audio amplifier 30 of direct current from the circuit powering the motor 6. Also a choke coil 33 is included in the circuit between the throttle 13 and the connection from the audio amplifier for the purpose of blocking flow of the audio frequency signal to the throttle direct-current circuit, which would drain energy from the audio frequency signal and overload the audio amplifier 30. The choke coil must be of sufficiently low resistance to enable the direct current to flow from the throttle through wire 14 to the motor 6 substantially unaltered. Since the audio frequency signal for driving the coil of speaker 23 is of alternating current character, it is immaterial as far as the speaker operation is concerned in which position the reversing switch 18 is set.

Bell

The portion of the circuit which produces the bell component of the audio frequency signal is within the dot-dash line enclosure of FIG. 1, labeled BELL. The bell tone is generated electronically by an oscillator 34 which is gated by a bell-gating multivibrator circuit 36. Such circuit produces intermittent bell-gating pulses from the outputs of both halves of the multivibrator. These pulses are properly shaped by resistance-capacitance networks to provide a wave shape that will closely simulate the rise and decay ofa bell tone.

The striking pattern of the bell can be regulated at will primarily by adjustment of the potentiometer 37 in one-half of the multivibrator circuit. The basic symmetry of the multivibrator can also be altered by opening or closing the switch 38 to the amount of resistance in the other half of the multivibrator circuit 36 primarily to vary the striking rate of the bell. Operation of these two controls provides sufficient variation of the ringing pattern and rate to simulate a wide range of bell ringing effects. The bell audio frequency component of the sound system passes to the mixer section 29 through the wire 39 when the bell tone on-off switch is in the on position shown in FIG. 1.

Escaping Steam Steam escaping from an engine produces several different types of sound, including the chuff of the exhaust from the steam engine when the engine is propelling the locomotive, the hiss of steam leakage and the blowoff effected automatically by opening ofa pop safety valve or intentionally in blowing down the boiler for cleaning it out. The sound of escaping steam is basically the same in all instances, and the circuit component for providing an audio frequency signal simulating escaping steam in the various instances mentioned is within the dot-dash line enclosure of FIG. 1 labeled STEAM.

The basic audio frequency for simulating the escape of steam is generated by a random noise or white noise generator circuit 41. This circuit will generate an audio frequency signal corresponding to a wide range of sound frequencies. To modify such audio frequency signal to simulate the sound of a steam engine exhaust a portion ofsuch signal is fed to the tone control and amplification circuits for exhaust designated 42 in FIG. 1, and then to the final stage exhaust amplifier 43 where it is gated to pulse in synchronism with the speed of rotation of the model train. The desired tone of the engine exhaust chuff can be selected by adjusting the exhaust tone control potentiometer 44, and the intensity of the exhaust sound can be altered by adjustment of the exhaust volume control potentiometer 45. The modified audio frequency signal for producing the simulated engine exhaust sound is impressed on the mixer section 29 by way ofwire 46.

Chuff Control Circuit Periodic interruption of the random noise audio frequency signal reaching the final stage exhaust amplifier 43 to simulate the chuff of a steam engine exhaust is accomplished by a radio frequency control circuit which effects electronic gating ofthe final stage exhaust amplifier. Such radio frequency signal is originated by the radio frequency oscillator 47. Such radio frequency signal passes to the detector circuit 49, then to the pulse generating and shaping circuits 50, and finally by way of wire 51 to the gate of the final stage exhaust amplifier 43.

A wire 52 is connected between the radio frequency oscillator 47 and the detector circuit 49 to a wire 14 connected to one of the rails 3 and 4, depending upon the position of the reversing switch 18. A capacitor 53 is interposed in wire 52 to block flow of direct current from the locomotive driving electric motor circuit to the oscillator 47 and detector 49. A radio frequency trap 54 including an inductance and capacitance in parallel forming a resonant circuit tuned to the frequency of oscillator 47 is interposed between the connection of wire 52 to wire 42 and the throttle 13 direct-current circuit for preventing the flow of radio frequency to the throttle circuit so as to avoid overloading the oscillator 47.

The radio frequency signal will pass from rail 3 through the tender frame 19, connector 20 and wire 21, to one contact 55 of a switch in the locomotive. The other switch contact 56 is connected by a wire 57 to the locomotive frame 22. which is in circuit with the other rail 4. When the radio frequency signal is continuous the signal at the gate of the final stage exhaust amplifier 43 prevents passage of an audio frequency signal through wire 46 to the mixer section 29. When the radio frequency signal generated by oscillator 47 is grounded by closing of switch 55,56, the detector 49 produces a gating pulse which triggers the final stage exhaust amplifier to transmit only a single pulse to the mixer section.

The switch contact 56 is raised into engagement with the stationary switch contact 55 when engaged by each corner of the square cam 58. Such a cam is mounted to turn with the locomotive driving wheels 2, so that the switch 55, 56 will be closed momentarily four times during each revolution of the driving wheels. Such switch closure produces a short circuit between the rails 3 and 4 for the radio frequency signal, so that each time the switch 55,56 closes the connection between the oscillator 47 and the detector circuit 49 is grounded through the wire 52, the switch short between the rails, and the ground wire 15. When the switch is closed, therefore, the final stage exhaust amplifier 43 is gated to allow passage of only a single audio frequency chuff signal from such amplifier by way ofwire 46 to the mixer section 29.

The shorting between rails 3 and 4 through switch 55,56 is effective with respect to the radio frequency gate control signal only, as described above, because the switch circuit has in it a capacitor 59, which blocks transmission of the direct current for energizing motor 6 from flowing through the switch 55,56 and bypassing the motor. Also a radio frequency trap in the form of the inductance-capacitance resonant circuit 60 tuned to the frequency of oscillator 47 is included in the lead 24 from the tender frame to the driving coil of speaker 23 so as to block flow of the radio frequency signal from the rail to the speaker coil. Such trap prevents the speaker coil from overloading the oscillator 47. It is not necessary to provide a radio frequency trap in wire 21 to block the radio frequency signal from reaching the motor 6 because the windings of such motor have sufficient inductance themselves to choke out the radio frequency signal.

The detector 49 generates one and only one pulse each time the switch 55,56 is closed in the locomotive. The pulsegenerating and shaping circuits 50 monitor the output of the detector circuit 49 and vary the amplitude, shape and decay rate of the pulse in such a manner as to provide a realistic chuff when fed as a gating pulse to the gate of the final stage exhaust amplifier 43. The cutoff control potentiometer 61 can be adjusted to vary the basic length of the exhaust pulse so as to produce a chuff which will simulate that produced either by a lightly loaded or a heavily loaded locomotive as the operator may prefer.

FIGS. 3 and 4 illustrate a communicating type of switch mechanism as an alternate to the switch 55,56 operated by the square cam 58 shown in FIG. 2. In FIG. 3 the wheel 2a engageable with track 3 is insulated from the locomotive frame 22. The wheel 2b which engages rail 4 is not insulated from the frame, but is connected electrically to it through the axle 9.

The wheel 2b has four sectors 58a of insulating material and the remainder of the Wheel including the portions 56a between the insulating sections are conductive and engage the rail 4. The sections 56a constitute one switch contact member.

A spring silver contact wire 55a is mounted to press lightly on the back of the uninsulated driver wheel 2b, but will touch conductive sections 56a of that wheel at only four locations between the insulating sectors 58a. Contact of the wire 55a with such uninsulated portions of the wheel 2b close the radio frequency shorting circuit between the rails 3 and 4.

The commutating type of switch construction shown in FIGS. 3 and 4 has practical advantages over the cam-operated switch mechanism of FIG. 2. Principally, engagement of the contact member 55a with the back of wheel 2b produces very little resistance to rotation of such wheel, and such resistance is uniform in all rotated positions of the wheel instead of the resistance varying with the rotative position of the wheel as in the case of the square cam shown in FIG. 2. Also the switch structure of FIGS. 3 and 4 is more economical to construct and can be installed readily on existing model locomotives to which the sound system accessory of the present invention is applied. 1 Whistle The circuitry for providing the whistle-simulating component of the audio frequency signal transmitted to the speaker 23 is within the dot-dash enclosure'of FIG. 1 labeled WHISTLE.

To produce an electronic audio frequency signal for simulating realistically the sound of a four-chime steam-operated whistle, four whistle-tone-generating oscillators, designated 62a, 62b, 62c and 62d in FIG. 1, are connected in parallel. By a variable resistance in each oscillator circuit the basic frequency of each individual oscillator can be set. Also, the basic tone of the whistle can be adjusted by altering in five increments the oscillator-operating voltage supplied by wire 64. Such voltage is altered by a five-position rotary switch 65.

The amplitude of the combined outputs of the whistle-tone generators 62a, 62b, 62c and 62d is varied by one potentiometer 66 of ganged potentiometers. The frequencies of the four oscillators are varied simultaneously by the other potentiometer 67. Both of the potentiometers 66 and 67 are adjusted simultaneously by swinging a controllever 68, common to the two potentiometers. Such whistle-control lever is shown on the stationary control panel of FIG. 5 and can be swung to provide whistle blast combinations of various types, such as the typical crossing warning whistle, for example.

In addition, a controlled amount of audio frequency signal simulating escaping steam is fed into the whistle component of the circuit by wire 69 connected to the mixer section 29 and to wire 71 leading to the random noise generator circuit 41. A tone control and amplification circuit for the hiss and whistle, designated 72, is interposed in the circuit 71. Such added steam hiss audio frequency component contributes greatly to the reality of the simulated steam whistle sound.

In addition, the lever 68 may be manipulated to control escaping steam sound simulating blowoff of steam occurring when a pop safety valve opens, or for blowing down the boiler. Such effect can be accomplished by moving hiss switch 73 from the of? position to the-on" position, in which latter position the whistle-tone oscillators are disconnected from the wire 69 leading to the audio-frequency mixer section 29 leaving only the steam hiss circuit connected to such mixer section. By manipulation of the lever 68 with the switch in this position, the intensity and duration of the steam blowoff sound can be controlled.

Portable Control Where the track system for a model railroad is extensive, it is desirable to enable the sound accessories described above to be operated by a portable control rather than from the stationary panel illustrated at the right of FIG. 5. Such a portable control, which may be called a walk-around unit, shown at the left in FIG. 5, can be held in the hand by a pistol grip 74. On the body of this portable control device various control elements are illustrated which are electrically connected in circuit with the corresponding controls on the stationary control panel, so that either control can be manipulated to obtain the desired effect.

Specifically, the portable control device includes the speed control potentiometer 17W for regulating the speed of travel of the locomotive when corresponding potentiometer 17 is in low speed position. Switch 18W can reverse the direction of travel of the locomotive in whichever position corresponding switch 18 is positioned on the stationary control panel. The bell can be energized or de-energized by manipulation of the switch 40W when the corresponding switch 40 on the stationary panel is in the off position. The sound of the chuff can be regulated by the control 61W, and its volume can be adjusted by the control W when the corresponding controls 61 and 45 on the stationary panel are in their full on positions. Blowofi of steam or whistle can be selected by the switch 73W, when the corresponding switch 73 on the stationary panel is in the on position. A whistle or blowoff can be controlled by pulling the trigger 68W when the lever 68 on the stationary control panel is in the full on position.

I claim:

1. A locomotive sound mechanism for a model train device comprising a locomotive, a speaker, and electronic audio frequency signal synthesizing means for generating an audio frequency signal generally matched to simulated locomotive sound and operable to drive said speaker for emitting such simulated locomotive sound and said electronic audio frequency signal synthesizing means being remote from the train device.

2. The locomotive sound mechanism defined in claim 1, in which the speaker is carried by the model train device.

3. The locomotive sound mechanism defined in claim 2, in which the locomotive is propelled by an electric motor to which driving current is supplied through rails on which the train device travels, and the audio frequency signal synthesized ,by the electronic audio frequency signal synthesizing means is transmitted to the speaker through the rails on which the train device travels.

4. The locomotive sound mechanism defined in claim 1, in which the audio frequency signal synthesized by the electronic audio frequency signal synthesizing means is generally matched to simulated locomotive sound including simulated locomotive bell sound.

5. The locomotive sound mechanism defined in claim 1, in which the audio frequency signal synthesized by the electronic audio frequency signal synthesizing means is generally matched to simulated locomotive sound including simulated locomotive whistle sound.

6. The locomotive sound mechanism defined in claim 5, in which the audio frequency signal synthesizing means includes a plurality of oscillators generally matched to different locomotive whistle sound frequencies, respectively, and means for combining the audio frequency signals produced by said plurality of oscillators.

7. The locomotive sound mechanism defined in claim 1, in which the audio frequency signal synthesized by the electronic audio frequency signal synthesizing means is generally matched to simulated locomotive sound including simulated combined locomotive whistle and escaping steam sound.

8. The locomotive sound mechanism defined in claim 1, in which the audio frequency signal synthesized by the electronic audio frequency signal synthesizing means is generally matched to simulated locomotive sound including simulated locomotive escaping steam sound.

9. The locomotive sound mechanism defined in claim 8, in which the escaping steam sound includes simulated engine exhaust chuffing.

10. The locomotive sound mechanism defined in claim 9, and timing means synchronized with the speed of the model train device for timing the simulated engine exhaust chuffing sound.

11. The locomotive sound mechanism defined in claim 10, in which the timing means is synchronized with the rotation of a wheel of the train device.

12. The locomotive sound mechanism defined in claim 11, in which the timing means includes commutating switch means.

13. The locomotive sound mechanism defined in claim 11, in which the timing means includes a radio frequency signal timing circuit transmitting a radio frequency signal to the train device.

14. The locomotive sound mechanism defined in claim 13, in which the radio frequency signal timing circuit includes rails on which the train device travels by way of which the radio frequency signal is transmitted to the train device.

15. The locomotive sound mechanism defined in claim 1, in which the audio frequency signal synthesized by the electronic audio frequency signal synthesizing means is generally matched to simulated locomotive sound including at least two separately generated audio frequency signals generally matched, respectively, to corresponding sounds selected from the group consisting of locomotive bell sound, locomotive whistle sound, escaping steam sound and engine exhaust chuffing.

16. The locomotive sound mechanism defined in claim 15, and integrating means for integrating separately generated audio frequency signals simulating different locomotive sounds to be impressed on the speaker.

17. The locomotive sound mechanism defined in claim 1, in which the audio frequency signal synthesizing means includes two components, one component being generally matched to simulated locomotive sound including simulated locomotive whistle sound and the other component being generally matched to simulated locomotive sound including escaping steam sound, actuating means, and means operable to condition said actuating means for controlling independently and selectively the component generally matched to simulated locomotive whistle sound and the component generally matched to simulated escaping steam sound. 

1. A locomotive sound mechanism for a model train device comprising a locomotive, a speaker, and electronic audio frequency signal synthesizing means for generating an audio frequency signal generally matched to simulated locomotive sound and operable to drive said speaker for emitting such simulated locomotive sound and said electronic audio frequency signal synthesizing means being remote from the train device.
 2. The locomotive sound mechanism defined in claim 1, in which the speaker is carried by the model train device.
 3. The locomotive sound mechanism defined in claim 2, in which the locomotive is propelled by an electric motor to which driving current is supplied through rails on which the train device travels, and the audio frequency signal synthesized by the electronic audio frequency signal synthesizing means is transmitted to the speaker through the rails on which the train device travels.
 4. The locomotive sound mechanism defined in claim 1, in which the audio frequency signal synthesized by the electronic audio frequency signal synthesizing means is generally matched to simulated locomotive sound including simulated locomotive bell sound.
 5. The locomotive sound mechanism defined in claim 1, in which the audio frequency signal synthesized by the electronic audio frequency signal synthesizing means is generally matched to simulated locomotive sound including simulated locomotive whistle sound.
 6. The locomotive sound mechanism defined in claim 5, in which the audio frequency signal synthesizing means includes a plurality of oscillators generally matched to different locomotive whistle sound frequencies, respectively, and means for combining the audio frequency signals produced by said plurality of oscillators.
 7. The locomotive sound mechanism defined in claim 1, in which the audio frequency signal synthesized by the electronic audio frequency signal synthesizing means is generally matched to simulated locomotive sound including simulated combined locomotive whistle and escaping steam sound.
 8. The locomotive sound mechanism defined in claim 1, in which the audio frequency signal synthesized by the electronic audio frequency signal synthesizing means is generally matched to simulated locomotive sound including simulated locomotive escaping steam sound.
 9. The locomotive sound mechanism defined in claim 8, in which the escaping steam sound includes simulated engine exhaust chuffing.
 10. The locomotive sound mechanism defined in claim 9, and timing means synchronized with the speed of the model train device for timing the simulated engine exhaust chuffing sound.
 11. The locomotive sound mechanism defined in claim 10, in which the timing means is synchronized with the rotation of a wheel of the train device.
 12. The locomotive sound mechanism defined in claim 11, in which the timing means includes commutating switch means.
 13. The locomotive sound mechanism defined in claim 11, in which the timing means includes a radio frequency signal timing circuit transmitting a radio frequency signal to the train device.
 14. The locomotive sound mechanism defined in claim 13, in which the radio frequency signal timing circuit includes rails on which the train device travels by way of which the radio frequency signal is transmitted to the train device.
 15. The locomotive sound mechanism defined in claim 1, in which the audio frequency signal synthesized by the electronic audio frequency signal synthesizing means is generally matched to simulated locomotive sound including at least two separately generated audio frequency signals generally matched, respectively, to corresponding sounds selected from the group consisting of locomotive bell sound, locomotive whistle sound, escaping steam sound and engine exhaust chuffing.
 16. The locomotive sound mechanism defined in claim 15, and integrating means for integrating separately generated audio frequency signals simulating different locomotive sounds to be impressed on the speaker.
 17. The locomotive sound mechanism defined in claim 1, in which the audio frequency signal synthesizing means includes two components, one component being generally matched to simulated locomotive sound including simulated locomotive whistle sound and the other component being generally matched to simulated locomotive sound including escaping steam sound, actuating means, and means operable to condition said actuating means for controlling independently and selectively the component generally matched to simulated locomotive whistle sound and the component generally matched to simulated escaping steam sound. 